The objectives of these studies is to determine how renal function is regulated by metabolic and hormonal mechanisms. The role of insulin or adrenalin in modulating renal function and metabolism in kidneys from normal, starved and diabetic animals is being probed. The simultaneous quantitative and qualitative relationships among renal substrate in the kidney and renal function are being determined. From these observations we plan to determine whether: a) the energy requirements for Na ion reabsorption varies, depending upon the type of renal function occurring; b) the metabolism of certain substrates (lactate or glucose) are selectively linked to the support of specific renal functions; c) the action of hormones, such as insulin and adrenalin, which regulate renal function, are dependent upon the presence of exogenous substrates and if so, which substrates; d) certain pathophysiological states such as starvation and diabetes change the characteristics of renal metabolism in relation to changes in function. By the use of the isolated perfused rat kidney preparation, the availability of substrates and of hormones can be varied independent of each other. Also, the rate of Na ion delivered to different nephron segments can be varied. From the simultaneous measurements of renal function and renal metabolism we may be able to gain insight into how the quantitative and qualitative aspects of substrate metabolism are linked to function and how insulin or adrenalin regulate renal function.